<!DOCTYPE html>
<title>
CSS opacity animation winning over web animation in delay phase creates
a stacking context
</title>
<style>
span {
  height: 100px;
  width: 100px;
  position: fixed;
  background: green;
  top: 50px;
}
@keyframes Opacity1 {
  from, to { opacity: 1; }
}
#test {
  width: 100px; height: 100px;
  background: blue;
  animation: Opacity1 100s;
}
</style>
<span></span>
<div id="test"></div>
<script>
  document.getElementById("test")
    .animate({ opacity: [0.1, 0.1] }, { duration: 100000, delay: 100000 });

  requestAnimationFrame(function() {
    document.documentElement.classList.remove("reftest-wait");
  });
</script>
